The use of conveyors, especially of the continuous belt type, for moving substrates through high throughput manufacturing units is well established. In the food industry, any contact between an item of food and any equipment surface, especially the conveyor, is a potential source of microbial contamination of the food. Furthermore contaminants on the surface of the food can be transferred to equipment leading to cross contamination of subsequent items. The nature of continuous belt conveyors tends to increase the risk of cross contamination, which is of particular concern in the food industry as it can lead to reduced shelf life of the contaminated food item, or even to food poisoning.
Conveyors can be wholly or partly enclosed within a decontaminating unit, for example as described in WO94/24875 (which is incorporated herein by reference) in which a plurality of UV sources are distributed around the walls of a tunnel and directed radially inwardly towards the centre of the cavity through which the substrate is conveyed. The equipment effectively decontaminates the conveyor and the substrate on the conveyor at the same time; although this simultaneous action is often highly desirable from the point of view of food hygiene, it is not universally permitted. Further, in use such equipment can occupy large areas of factory floor, partly because the requirement for ensuring operator safety often entails providing additional features.
Such equipment is effective in minimising the effect of cross contamination between belt and substrate, provided especially that the conveyor belt is apertured or UV transmissive. If the belt is neither apertured nor UV transmissive, decontamination of the underside of the belt can be less effective. Even with belts that are substantially apertured, such as conveyors with belts of interlocking metal or plastic mesh, some contamination can build up in small crevices that are inevitably present in practice, particularly at the flexible nodes of the mesh.